Goldfish Barrelponics Update 1

I have had a barrel with ten shubunkin goldfish for a little under two years.  Time really flies.  I think it is time to do an update on how things are going after this time.  

One barrel with ten goldfish is WAY overstocked.  With normal filtration and weekly water changes this system would have crashed and some fish would have died by now.   

I don't do water changes in the barrel any more, yet the fish are growing, laying eggs, and even though there is a lot of sun on the barrel the water is usually clear.  These goldfish are growing large, and produce a lot of waste, yet the water is clean enough that they lay eggs.  

The only reason that this is working is because the water is being cleaned by plants.  This is very simple aquaponics on a small scale.  Aquaponics in a barrel = barrelponics.  

How Barrelponics works: 

• I feed the fish (some fish food, but also duckweed and azolla);
• the fish produce waste in the water;
• the nutrient rich dirty water is pumped through a gravel pot;
• bacteria living on the gravel convert the fish waste to less toxic substances; 
• plants growing in the gravel extract the nutrients from the water;
• cleaner water returns to the barrel;  
• the cleaner water is aerated as it splashes back into the barrel.

Vietnamese coriander taking over aquaponics

I bought a cheap solar pond pump.  This pump runs when the sun is shining, and stops overnight or when it is cloudy.  As the pump is at the bottom of the barrel it is pumping water from lower down in the water column, this gets cleaned by plants and is aerated as it enters the top of the barrel, this ensures that water is circulating through the entire barrel.

Over winter we may have weeks of cloudy weather where the pump does not turn on.  During this time the water is cold, and the fish are not very acting nor are they eating much or producing much waste.  Cold water holds more oxygen than warm water, and the fish use less oxygen when they are cold.

During summer the fish are very active, eating a lot, laying eggs, and producing a lot of waste.  Being hot means the water holds less oxygen, plus the fish and plants are both taking a lot of oxygen from the water.  During this time the pump is on all day, oxygenating the water.  Plants grow faster in warmer weather, so they are extract more waste from the water during this time.

I am pumping the water through a 2L plastic milk bottle filled with drainage gravel.  You could easily use something that looks nicer than a milk bottle, or different gravel, but I wanted to keep this cheap.  The plants are growing in the gravel are plants I already grew elsewhere.  It is very low tech and very cheap.

It is a good little system.  Other than feeding the fish, occasionally topping up the water in the barrel, harvesting herbs and things, and enjoying watching the fish, I don't do anything.  

Vietnamese coriander, Brahmi, and water celery

My barrelponics is intended to clean the water, any herbs or vegetables produced is just a bonus.  For this reason I am growing whatever grows and clears the water best.  I have vegetable gardens to produce food, this is just a filter.  

I also have a small floating pot of herbs in the water.  It has roots extending into the water.  The plants grow well and I have to cut it back from time to time.  I don't think this is doing anywhere near as much as the milk bottle when it comes to cleaning the water, but every little bit helps.  It is also nice for the fish to have roots to swim through, and insects see to live among the roots and are eaten by my fish.

I also grow duckweed and azolla in the barrel.  The fish tend to eat this and I have to add more from time to time, so it is more for their food than cleaning their water.  Duckweed and azolla are great because if we are going away I can put a few extra scoops of azolla and duckweed in the barrel and I know that the fish have high quality food while I am away.  Unlike bought food, azolla and duckweed won't foul the water, the fish won't over eat no matter how much is in there, it lasts longer because it reproduces, and it is high quality natural feed for the fish.

Azolla, duckweed, and floating pot of herbs

It's almost like a waterfall in there

The fish are growing - the water needs topping up

I originally planted a bunch of different plants in the barrelponics to see what works best in my climate over a longer term.  I expected some to perform well over summer, and other to perform best over winter.  Out of all of them the Vietnamese coriander (Persicaria odorata) thrives the best all year and pretty much took over.  

If you look closely you can see that there are still a few different things in the pot, but not many of them.  The Vietnamese coriander does not grow over winter in the garden, and slows growth over summer in the garden, but in aquaponics it grows all year and absolutely thrives during warmer weather.

Over winter I leave the shabby growth.  We get some hard frosts and this partly dead stuff protects the plants from freezing.  Once the weather warmed I cut all that off and let everything grow anew.

Goldfish Barrelponics over winter 

Over summer most of the barrelponic plants grow very fast.  I mostly grow leafy things as they use a lot of nitrogen, but have tried a few fruiting vegetables with limited success.

This post seems to be getting a bit too long, so I will stop here.  If you are interested I will write a second update about different plants I tried in barrelponics.  Some worked for me, while others didn't.